151
Multiplying a two-digit number
Textbook: Part 4, lesson 141, pp. 54–55
GoalMultiply a two-digit number by a one-digit number using the distributive law.
New words
two-digit number · ikki xonali sonone-digit number · bir xonali sondistributive law · taqsimot qonuniproduct · ko‘paytma
Explanation
We split the two-digit number into its place-value parts and multiply each. 15 × 6 = (10 + 5) × 6 = 10 × 6 + 5 × 6 = 60 + 30 = 90. First multiply the tens, then the ones, then add the results.
Worked examples
27 × 7 = (20 + 7) × 7 = 140 + 49 = 189.
38 × 9 = 30 × 9 + 8 × 9 = 270 + 72 = 342.
Class activity
“Grid rectangle”: draw a rectangle for 15 × 6 on squared paper: colour the 10-square part and the 5-square part differently. Children add the two areas (60 and 30) to get 90.
Practice
1
15 × 6 = ?
90
2
27 × 7 = ?
189
3
45 × 3 = ?
135
4
38 × 9 = ?
342
5
A class has 32 pupils. Dentists gave each pupil 3 toothbrushes. How many toothbrushes were given in all?
96